1 /*
2 * Copyright (c) 1997, 2025, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #ifndef SHARE_ASM_ASSEMBLER_HPP
26 #define SHARE_ASM_ASSEMBLER_HPP
27
28 #include "asm/codeBuffer.hpp"
29 #include "asm/register.hpp"
30 #include "code/oopRecorder.hpp"
31 #include "code/relocInfo.hpp"
32 #include "memory/allocation.hpp"
33 #include "utilities/checkedCast.hpp"
34 #include "utilities/debug.hpp"
35 #include "utilities/growableArray.hpp"
36 #include "utilities/macros.hpp"
37
38 // This file contains platform-independent assembler declarations.
39
40 class MacroAssembler;
41 class AbstractAssembler;
42 class Label;
43
44 /**
45 * Labels represent destinations for control transfer instructions. Such
46 * instructions can accept a Label as their target argument. A Label is
47 * bound to the current location in the code stream by calling the
48 * MacroAssembler's 'bind' method, which in turn calls the Label's 'bind'
49 * method. A Label may be referenced by an instruction before it's bound
50 * (i.e., 'forward referenced'). 'bind' stores the current code offset
51 * in the Label object.
52 *
53 * If an instruction references a bound Label, the offset field(s) within
54 * the instruction are immediately filled in based on the Label's code
55 * offset. If an instruction references an unbound label, that
56 * instruction is put on a list of instructions that must be patched
57 * (i.e., 'resolved') when the Label is bound.
58 *
59 * 'bind' will call the platform-specific 'patch_instruction' method to
60 * fill in the offset field(s) for each unresolved instruction (if there
61 * are any). 'patch_instruction' lives in one of the
62 * cpu/<arch>/vm/assembler_<arch>* files.
63 *
64 * Instead of using a linked list of unresolved instructions, a Label has
65 * an array of unresolved instruction code offsets. _patch_index
66 * contains the total number of forward references. If the Label's array
67 * overflows (i.e., _patch_index grows larger than the array size), a
68 * GrowableArray is allocated to hold the remaining offsets. (The cache
69 * size is 4 for now, which handles over 99.5% of the cases)
70 *
71 * Labels may only be used within a single CodeSection. If you need
72 * to create references between code sections, use explicit relocations.
73 */
74 class Label {
75 private:
76 enum { PatchCacheSize = 4 DEBUG_ONLY( +4 ) };
77
78 // _loc encodes both the binding state (via its sign)
79 // and the binding locator (via its value) of a label.
80 //
81 // _loc >= 0 bound label, loc() encodes the target (jump) position
82 // _loc == -1 unbound label
83 int _loc;
84
85 // References to instructions that jump to this unresolved label.
86 // These instructions need to be patched when the label is bound
87 // using the platform-specific patchInstruction() method.
88 //
89 // To avoid having to allocate from the C-heap each time, we provide
90 // a local cache and use the overflow only if we exceed the local cache
91 int _patches[PatchCacheSize];
92 int _patch_index;
93 GrowableArray<int>* _patch_overflow;
94
95 NONCOPYABLE(Label);
96 protected:
97
98 // The label will be bound to a location near its users.
99 bool _is_near;
100
101 #ifdef ASSERT
102 // Sourcre file and line location of jump instruction
103 int _lines[PatchCacheSize];
104 const char* _files[PatchCacheSize];
105 #endif
106 public:
107
108 /**
109 * After binding, be sure 'patch_instructions' is called later to link
110 */
111 void bind_loc(int loc) {
112 assert(loc >= 0, "illegal locator");
113 assert(_loc == -1, "already bound");
114 _loc = loc;
115 }
116 void bind_loc(int pos, int sect) { bind_loc(CodeBuffer::locator(pos, sect)); }
117
118 #ifndef PRODUCT
119 // Iterates over all unresolved instructions for printing
120 void print_instructions(MacroAssembler* masm) const;
121 #endif // PRODUCT
122
123 /**
124 * Returns the position of the Label in the code buffer
125 * The position is a 'locator', which encodes both offset and section.
126 */
127 int loc() const {
128 assert(_loc >= 0, "unbound label");
129 return _loc;
130 }
131 int loc_pos() const { return CodeBuffer::locator_pos(loc()); }
132 int loc_sect() const { return CodeBuffer::locator_sect(loc()); }
133
134 bool is_bound() const { return _loc >= 0; }
135 bool is_unbound() const { return _loc == -1 && _patch_index > 0; }
136 bool is_unused() const { return _loc == -1 && _patch_index == 0; }
137
138 // The label will be bound to a location near its users. Users can
139 // optimize on this information, e.g. generate short branches.
140 bool is_near() { return _is_near; }
141
142 /**
143 * Adds a reference to an unresolved displacement instruction to
144 * this unbound label
145 *
146 * @param cb the code buffer being patched
147 * @param branch_loc the locator of the branch instruction in the code buffer
148 */
149 void add_patch_at(CodeBuffer* cb, int branch_loc, const char* file = nullptr, int line = 0);
150
151 /**
152 * Iterate over the list of patches, resolving the instructions
153 * Call patch_instruction on each 'branch_loc' value
154 */
155 void patch_instructions(MacroAssembler* masm);
156
157 void init() {
158 _loc = -1;
159 _patch_index = 0;
160 _patch_overflow = nullptr;
161 _is_near = false;
162 }
163
164 Label() {
165 init();
166 }
167
168 ~Label() {
169 assert(is_bound() || is_unused(), "Label was never bound to a location, but it was used as a jmp target");
170 }
171
172 void reset() {
173 init(); //leave _patch_overflow because it points to CodeBuffer.
174 }
175 };
176
177 // A NearLabel must be bound to a location near its users. Users can
178 // optimize on this information, e.g. generate short branches.
179 class NearLabel : public Label {
180 public:
181 NearLabel() : Label() { _is_near = true; }
182 };
183
184 // A union type for code which has to assemble both constant and
185 // non-constant operands, when the distinction cannot be made
186 // statically.
187 class RegisterOrConstant {
188 private:
189 Register _r;
190 intptr_t _c;
191
192 public:
193 RegisterOrConstant(): _r(noreg), _c(0) {}
194 RegisterOrConstant(Register r): _r(r), _c(0) {}
195 RegisterOrConstant(intptr_t c): _r(noreg), _c(c) {}
196
197 Register as_register() const { assert(is_register(),""); return _r; }
198 intptr_t as_constant() const { assert(is_constant(),""); return _c; }
199
200 Register register_or_noreg() const { return _r; }
201 intptr_t constant_or_zero() const { return _c; }
202
203 bool is_register() const { return _r != noreg; }
204 bool is_constant() const { return _r == noreg; }
205 };
206
207 // The Abstract Assembler: Pure assembler doing NO optimizations on the
208 // instruction level; i.e., what you write is what you get.
209 // The Assembler is generating code into a CodeBuffer.
210 class AbstractAssembler : public ResourceObj {
211 friend class Label;
212
213 protected:
214 CodeSection* _code_section; // section within the code buffer
215 OopRecorder* _oop_recorder; // support for relocInfo::oop_type
216
217 public:
218 // Code emission & accessing
219 address addr_at(int pos) const { return code_section()->start() + pos; }
220
221 protected:
222 // This routine is called with a label is used for an address.
223 // Labels and displacements truck in offsets, but target must return a PC.
224 address target(Label& L) { return code_section()->target(L, pc()); }
225
226 bool is8bit(int x) const { return -0x80 <= x && x < 0x80; }
227 bool isByte(int x) const { return 0 <= x && x < 0x100; }
228 bool isShiftCount(int x) const { return 0 <= x && x < 32; }
229
230 // Mark instruction boundaries, this is required when emitting relocatable values.
231 // Basically, all instructions that directly or indirectly use Assembler::emit_data* methods.
232 class InstructionMark: public StackObj {
233 private:
234 AbstractAssembler* _assm;
235
236 public:
237 InstructionMark(AbstractAssembler* assm) : _assm(assm) {
238 assert(assm->inst_mark() == nullptr, "overlapping instructions");
239 _assm->set_inst_mark();
240 }
241 ~InstructionMark() {
242 _assm->clear_inst_mark();
243 }
244 };
245 friend class InstructionMark;
246
247 public:
248 // count size of instructions which are skipped from inline heuristics
249 class InlineSkippedInstructionsCounter: public StackObj {
250 private:
251 AbstractAssembler* _assm;
252 address _start;
253 public:
254 InlineSkippedInstructionsCounter(AbstractAssembler* assm) : _assm(assm), _start(assm->pc()) {
255 }
256 ~InlineSkippedInstructionsCounter() {
257 _assm->register_skipped(checked_cast<int>(_assm->pc() - _start));
258 }
259 };
260
261 protected:
262 #ifdef ASSERT
263 // Make it return true on platforms which need to verify
264 // instruction boundaries for some operations.
265 static bool pd_check_instruction_mark();
266
267 // Add delta to short branch distance to verify that it still fit into imm8.
268 int _short_branch_delta;
269
270 int short_branch_delta() const { return _short_branch_delta; }
271 void set_short_branch_delta() { _short_branch_delta = 32; }
272 void clear_short_branch_delta() { _short_branch_delta = 0; }
273
274 class ShortBranchVerifier: public StackObj {
275 private:
276 AbstractAssembler* _assm;
277
278 public:
279 ShortBranchVerifier(AbstractAssembler* assm) : _assm(assm) {
280 assert(assm->short_branch_delta() == 0, "overlapping instructions");
281 _assm->set_short_branch_delta();
282 }
283 ~ShortBranchVerifier() {
284 _assm->clear_short_branch_delta();
285 }
286 };
287 #else
288 // Dummy in product.
289 class ShortBranchVerifier: public StackObj {
290 public:
291 ShortBranchVerifier(AbstractAssembler* assm) {}
292 };
293 #endif
294
295 // sign-extended tolerant cast needed by callers of emit_int8 and emit_int16
296 // Some callers pass signed types that need to fit into the unsigned type so check
297 // that the range is correct.
298 template <typename T>
299 constexpr T narrow_cast(int x) const {
300 if (x < 0) {
301 using stype = std::make_signed_t<T>;
302 assert(x >= std::numeric_limits<stype>::min(), "too negative"); // >= -128 for 8 bits
303 return static_cast<T>(x); // cut off sign bits
304 } else {
305 return checked_cast<T>(x);
306 }
307 }
308
309 public:
310
311 // Creation
312 AbstractAssembler(CodeBuffer* code);
313
314 // ensure buf contains all code (call this before using/copying the code)
315 void flush();
316
317 void emit_int8( int x1) { code_section()->emit_int8(narrow_cast<uint8_t>(x1)); }
318
319 void emit_int16( int x) { code_section()->emit_int16(narrow_cast<uint16_t>(x)); }
320
321 void emit_int16( int x1, int x2) { code_section()->emit_int16(narrow_cast<uint8_t>(x1),
322 narrow_cast<uint8_t>(x2)); }
323
324 void emit_int24( int x1, int x2, int x3) { code_section()->emit_int24(narrow_cast<uint8_t>(x1),
325 narrow_cast<uint8_t>(x2),
326 narrow_cast<uint8_t>(x3)); }
327
328 void emit_int32( uint32_t x) { code_section()->emit_int32(x); }
329 void emit_int32( int x1, int x2, int x3, int x4) { code_section()->emit_int32(narrow_cast<uint8_t>(x1),
330 narrow_cast<uint8_t>(x2),
331 narrow_cast<uint8_t>(x3),
332 narrow_cast<uint8_t>(x4)); }
333
334 void emit_int64( uint64_t x) { code_section()->emit_int64(x); }
335
336 void emit_float( jfloat x) { code_section()->emit_float(x); }
337 void emit_double( jdouble x) { code_section()->emit_double(x); }
338 void emit_address(address x) { code_section()->emit_address(x); }
339
340 enum { min_simm10 = -512 };
341
342 // Test if x is within signed immediate range for width.
343 static bool is_simm(int64_t x, uint w) {
344 precond(1 < w && w < 64);
345 int64_t limes = INT64_C(1) << (w - 1);
346 return -limes <= x && x < limes;
347 }
348
349 static bool is_simm8(int64_t x) { return is_simm(x, 8); }
350 static bool is_simm9(int64_t x) { return is_simm(x, 9); }
351 static bool is_simm10(int64_t x) { return is_simm(x, 10); }
352 static bool is_simm16(int64_t x) { return is_simm(x, 16); }
353 static bool is_simm32(int64_t x) { return is_simm(x, 32); }
354
355 // Test if x is within unsigned immediate range for width.
356 static bool is_uimm(uint64_t x, uint w) {
357 precond(0 < w && w < 64);
358 uint64_t limes = UINT64_C(1) << w;
359 return x < limes;
360 }
361
362 static bool is_uimm12(uint64_t x) { return is_uimm(x, 12); }
363 static bool is_uimm32(uint64_t x) { return is_uimm(x, 32); }
364
365 // Accessors
366 CodeSection* code_section() const { return _code_section; }
367 CodeBuffer* code() const { return code_section()->outer(); }
368 int sect() const { return code_section()->index(); }
369 address pc() const { return code_section()->end(); }
370 address begin() const { return code_section()->start(); }
371 int offset() const { return code_section()->size(); }
372 int locator() const { return CodeBuffer::locator(offset(), sect()); }
373
374 OopRecorder* oop_recorder() const { return _oop_recorder; }
375 void set_oop_recorder(OopRecorder* r) { _oop_recorder = r; }
376
377 void register_skipped(int size) { code_section()->register_skipped(size); }
378
379 address inst_mark() const { return code_section()->mark(); }
380 void set_inst_mark() { code_section()->set_mark(); }
381 void set_inst_mark(address addr) { code_section()->set_mark(addr); }
382 void clear_inst_mark() { code_section()->clear_mark(); }
383 void set_inst_end(address addr) { code_section()->set_end(addr); }
384
385 // Constants in code
386 void relocate(RelocationHolder const& rspec, int format = 0) {
387 assert(!pd_check_instruction_mark()
388 || inst_mark() == nullptr || inst_mark() == code_section()->end(),
389 "call relocate() between instructions");
390 code_section()->relocate(code_section()->end(), rspec, format);
391 }
392 void relocate( relocInfo::relocType rtype, int format = 0) {
393 code_section()->relocate(code_section()->end(), rtype, format);
394 }
395 void relocate(address addr, relocInfo::relocType rtype, int format = 0) {
396 code_section()->relocate(addr, rtype, format);
397 }
398 void relocate(address addr, RelocationHolder const& rspec, int format = 0) {
399 code_section()->relocate(addr, rspec, format);
400 }
401
402 static int code_fill_byte(); // used to pad out odd-sized code buffers
403
404 // Associate a comment with the current offset. It will be printed
405 // along with the disassembly when printing nmethods. Currently
406 // only supported in the instruction section of the code buffer.
407 void block_comment(const char* comment);
408 // Copy str to a buffer that has the same lifetime as the CodeBuffer
409 const char* code_string(const char* str);
410
411 // Label functions
412 void bind(Label& L); // binds an unbound label L to the current code position
413
414 // Move to a different section in the same code buffer.
415 void set_code_section(CodeSection* cs);
416
417 // Inform assembler when generating stub code and relocation info
418 address start_a_stub(int required_space);
419 void end_a_stub();
420 // Ditto for constants.
421 address start_a_const(int required_space, int required_align = sizeof(double));
422 void end_a_const(CodeSection* cs); // Pass the codesection to continue in (insts or stubs?).
423
424 // constants support
425 //
426 // We must remember the code section (insts or stubs) in c1
427 // so we can reset to the proper section in end_a_const().
428 address int_constant(jint c) {
429 CodeSection* c1 = _code_section;
430 address ptr = start_a_const(sizeof(c), sizeof(c));
431 if (ptr != nullptr) {
432 emit_int32(c);
433 end_a_const(c1);
434 }
435 return ptr;
436 }
437 address long_constant(jlong c) {
438 CodeSection* c1 = _code_section;
439 address ptr = start_a_const(sizeof(c), sizeof(c));
440 if (ptr != nullptr) {
441 emit_int64(c);
442 end_a_const(c1);
443 }
444 return ptr;
445 }
446 address double_constant(jdouble c) {
447 CodeSection* c1 = _code_section;
448 address ptr = start_a_const(sizeof(c), sizeof(c));
449 if (ptr != nullptr) {
450 emit_double(c);
451 end_a_const(c1);
452 }
453 return ptr;
454 }
455 address float_constant(jfloat c) {
456 CodeSection* c1 = _code_section;
457 address ptr = start_a_const(sizeof(c), sizeof(c));
458 if (ptr != nullptr) {
459 emit_float(c);
460 end_a_const(c1);
461 }
462 return ptr;
463 }
464 address address_constant(address c) {
465 CodeSection* c1 = _code_section;
466 address ptr = start_a_const(sizeof(c), sizeof(c));
467 if (ptr != nullptr) {
468 emit_address(c);
469 end_a_const(c1);
470 }
471 return ptr;
472 }
473 address address_constant(address c, RelocationHolder const& rspec) {
474 CodeSection* c1 = _code_section;
475 address ptr = start_a_const(sizeof(c), sizeof(c));
476 if (ptr != nullptr) {
477 relocate(rspec);
478 emit_address(c);
479 end_a_const(c1);
480 }
481 return ptr;
482 }
483 address array_constant(const GrowableArray<jbyte>* c, int alignment) {
484 CodeSection* c1 = _code_section;
485 address ptr = start_a_const(c->length(), alignment);
486 if (ptr != nullptr) {
487 for (int i = 0; i < c->length(); i++) {
488 emit_int8(c->at(i));
489 }
490 end_a_const(c1);
491 }
492 return ptr;
493 }
494
495 // Bang stack to trigger StackOverflowError at a safe location
496 // implementation delegates to machine-specific bang_stack_with_offset
497 void generate_stack_overflow_check( int frame_size_in_bytes );
498 virtual void bang_stack_with_offset(int offset) = 0;
499
500
501 /**
502 * A platform-dependent method to patch a jump instruction that refers
503 * to this label.
504 *
505 * @param branch the location of the instruction to patch
506 * @param masm the assembler which generated the branch
507 */
508 void pd_patch_instruction(address branch, address target, const char* file, int line);
509
510 };
511
512 #include CPU_HEADER(assembler)
513
514 #endif // SHARE_ASM_ASSEMBLER_HPP